1. Field of the Invention
The present invention relates to a photosensitive resin composition. More particularly, the present invention relates to a photosensitive resin composition useful for forming protective or insulating films for, for example, semiconductor devices, flat panel displays, liquid crystal devices, and especially for color filters and thin film transistors (hereinafter referred to as xe2x80x9cTFTsxe2x80x9d) etc.
2. Related Art
Heretofore, mixtures of novolak resins and diazidonaphthoquinone have generally been used as positive photoresists useful in the production of flat panel displays (hereinafter referred to as xe2x80x9cFPDsxe2x80x9d) or semiconductor devices. However, films formed by using these mixtures are sometimes insufficient in transparency. In case these films are intended to use as protective or insulating films which are applied to the surfaces of semiconductor devices, FPDs or liquid crystal devices, such insufficient transparency causes disadvantageousness. In particular, some problems occur due to such insufficient transparency when these films are used for such devices as color filters or TFTs through which light is allowed to pass. Why these conventional photoresist films cannot have sufficiently high transparency is chiefly due to the nature of novolak resins used as resin components in the photoresists. In case high transparency is required for such films, acrylic or polyhydroxystyrene (hereinafter referred to as xe2x80x9cPHSxe2x80x9d) resins which can give films having higher transparency have been used. However, even in this case, some improvements other than its transparency are needed.
Namely, since acrylic or PHS resins are poor in compatibility with copolymers of benzophenone compounds and 1,2-diazidonaphthoquinone, which are photosensitizers usually used in photoresists to be used for the above-described purposes, it is sometimes difficult to obtain high contrast between exposed area and unexposed area after development.
Therefore, photosensitive resin compositions capable of forming films having sufficiently high transparency, and of imparting satisfactorily high contrast to images to be formed in the films after development are still needed.
A photosensitive resin composition of the present invention comprises the following components:
(a) a photosensitizer having in its structure 1,2-diazidonaphthoquinone structure, and a methylene-bridged structure composed of two or more methyl-substituted phenol derivatives;
(b) a polymer having both hydroxyl group and carboxyl group, or a combination of a polymer having hydroxyl group and a polymer having carboxyl group;
(c) a crosslinking agent capable of crosslinking hydroxyl group and carboxyl group; and
(d) a solvent.
Further, an article of the present invention comprises a protective or insulating film made from the aforementioned photosensitive resin composition.
Moreover, a method for forming patterns of the present invention comprises the following process;
(a) a process for coating the aforementioned photosensitive resin composition on a substrate,
(b) a process for exposing the coated photosensitive resin composition on the substrate for making an image on it; and
(c) a process for developing the exposed photosensitive resin composition on the substrate.
Furthermore, an another aspect of the present invention is an use of the aforementioned photosensitive resin composition for manufacturing a protective or insulating film.
By using the photosensitive resin composition of the present invention, it is possible to obtain films having high transparency. Moreover, patterns having high contrast can be obtained when the composition of the invention is used as a photoresist.
1. Photosensitizer
The photosensitizer for use in the photosensitive resin composition of the present invention has in its structure 1,2-diazidonaphthoquinone structure and a methylene-bridged structure composed of two or more methyl-substituted phenol derivatives. In general, methyl-substituted phenol derivatives are phenol derivatives in which any of hydrogens attached to carbons on phenol structure is substituted with methyl group. However, in the present invention, they also encompass those compounds which are not substituted with methyl group, that is, phenols themselves. Therefore, the methylene-bridged structure composed of two or more methyl-substituted phenol derivatives can be defined as a structure in which two or more phenol structures are connected by methylene group, and any of hydrogens on the phenol structure is substituted with methyl group.
In the present invention, the photosensitizer has in its structure two or more methyl-substituted phenol derivatives; and the number of the methyl-substituted phenol derivatives present in the structure is preferably from 2 to 5, particularly 4.
In the present invention, the photosensitizer may contain a plurality of 1,2-diazidonaphthoquinone structures. It is enough that at least one 1,2-diazidonaphthoquinone structure is present in the structure of the photosensitizer. However, this structure can exist in any number, the maximum number being equal to the number of hydroxyl groups present in the methylene-bridged structure composed of methyl-substituted phenol derivatives; the number is preferably from 1 to 5, particularly from 2 to 4.
Of photosensitizers fulfilling the above-described requirements, those ones represented by the following formulae are particularly preferred as the photosensitizer for use in the photosensitive resin composition of the present invention: 
wherein D is 
or H, provided that at least one of Ds present in each formula is not H.
Of the photosensitizers re presented by the above formulae, those ones in which three of four Ds are esterified with 1,2-diazidonaphthoquinonesulfonic acid are most preferred.
Such photosensitizers can be obtained by condensation polymerization reaction between methylene-bridged products of methyl-substituted phenol derivatives and compounds having 1,2-diazidonaphthoquinone structure; and polymers obtained in this manner are preferred.
Any methyl-substituted phenol derivative and any compound having 1,2-diazidonaphthoquinone structure can be used for the condensation polymerization as long as they can give, when condensation-polymerized, a photosensitizer that can be used for the photosensitive resin composition of the present invention. Further, this condensation polymerization reaction can be carried out by any conventional method.
Examples of compounds having 1,2-diazidonaphthoquinone structure that can be subjected to the above condensation polymerization include 1,2-diazidobenzoquinonesulfonic ester, 1,2-diazidonaphthoquinonesulfonic ester, 1,2-diazidobenzo-quinonesulfonamide, and 1,2-diazidonaphthoquinonesulfonamide. More specifically, the following compounds can be mentioned: phenyl 1,2-diazidobenzoquinone-4-sulfonate, 1,2,1xe2x80x21,2xe2x80x2-di-(diazidobenzoquinone-4-sulfonyl)-dihydroxybiphenyl, 1,2-diazidobenzoquinone-4-(N-ethyl-N-xcex2-naphthyl)-sulfonamide, cyclohexyl 1,2-diazidonaphthoquinone-5-sulfonate, 1-(1,2-diazidonaphthoquinone-5-sulfonyl) -3,5-dimethylpyrazole, 1,2-diazidonaphthoquinone-5-sulfonic acid-4xe2x80x2-hydroxy-diphenyl-4xe2x80x3-azo-xcex2-naphthol ester, N,N-di-(1,2-diazidonaphthoquinone-5-sulfonyl)-aniline, 2xe2x80x2-(1,2-diazidonaphthoquinone-5-sulfonyloxy)-1-hydroxyanthraquinone, 1,2-diazidonaphthoquinone-5-sulfonic acid-2,3,4-trihydroxy-benzophenone ester, 1,2-diazidonaphthoquinone-5-(N-dihyroabietyl)sulfonamide, a condensation product of 1,2-diazidonaphthoquinone-5-sulfonic acid chloride(2 moles) and 4,4xe2x80x2-diaminobenzophenone (1 mole), a condensation product of 1,2-diazidonaphthoquinone-5-sulfonic acid chloride (2 moles) and 4,4xe2x80x2-dihydroxy-1,1xe2x80x2-diphenylsulfone (1 mole), and a condensation product of 1,2-diazidonaphthoquinone-5-sulfonic acid chloride (1 mole) and purpurogallin (1 mole). In addition, the compounds having 1,2-diazidonaphthoquinone structure described in the following documents may also be used: Japanese Patent Publications No. 1953/1962, No. 3627/1962, No. 13109/1962, No. 26126/1965, No. 3801/1965, No. 5604/1970, No. 27345/1970 and No. 13013/1976; Japanese Patent Laid-Open Publications No. 96575/1973, No. 63802/1973 and No. 63803/1973; J. Kosar, xe2x80x9cLight-Sensitive Systemsxe2x80x9d, 339-352 (1965), John Wiley and Sons, New York, U.S.A.; W. S. De Forest, xe2x80x9cPhotoresistxe2x80x9d, 50 (1975), McGraw-Hill, Inc., New York, U.S.A., and the like. (These documents are cited as a part of disclosures of this specification.)
Examples of methylene-bridged products of methyl-substituted phenol derivatives that can be used for the above-described condensation polymerization include bisparacresol-bis-2,5-xylenol, bisphenol-bis-2,5-xylenol and bisparacresol-bis-orthocresol etc.
Two or more of these photosensitizers may be used in combination, if necessary. Moreover, photosensitizers not included in the above-described categories can also be used in combination with the above photosensitizers within such limits that the effects of the invention will not be marred.
The percentage of the photosensitizer in the photosensitive resin composition of the present invention is from 3 to 50%, preferably from 5 to 35% of the weight of the polymer contained in the photosensitive resin composition. By using the photosensitizer within the above-described range, it is possible to obtain a sufficient sensitivity and a satisfactory resolution.
2. Polymer
The photosensitive resin composition of the present invention comprises as its binder an alkali-soluble polymer.
In a first embodiment of the present invention, the photosensitive resin composition comprises as the alkali-soluble polymer a polymer having both hydroxyl group and carboxyl group. Any polymer of this type can be used for the photosensitive resin composition of the present invention. However, the OH value of the polymer is preferably from 10 to 180, more preferably from 50 to 120; and the acid value of the polymer is preferably from 10 to 200, more preferably from 30 to 150.
Further, the polymer for use in the photosensitive resin composition of the present invention is preferably an acrylic or polyhydroxystyrene polymer. These polymers can be obtained by using as a monomer an acrylic acid derivative or hydroxystyrene derivative.
Such a polymer can be obtained by copolymerizing an unsaturated monomer having hydroxyl group (A1) and a monomer having carboxyl group (A2), or by homopolymerizing a monomer having both hydroxyl group and carboxyl group (A). A monomer (B) other than these monomers may also be copolymerized as needed.
Examples of monomers having hydroxyl group (A1) include hydroxystyrene derivatives, hydroxyalkyl (meth)acrylate derivatives and vinyl alcohol derivatives etc. Specific examples of such monomers include hydroxystyrene, hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate and vinyl alcohol etc.
It is herein noted that (meth)acrylate means both acrylate and methacrylate and that (meth)acrylic acid means both acrylic acid and methacrylic acid.
Examples of monomers having carboxyl group (A2) include xcex1,xcex2-ethylenically unsaturated carboxylic acid derivatives. In the present invention, the carboxyl group is one derived from any of monocarboxylic acids, dicarboxylic acids, acid anhydrides, monoesters of dicarboxylic acids, and diesters of dicarboxylic acids. Specific examples of these compounds include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, monomethyl maleate, monomethyl fumarate, monoethyl citraconate, maleic anhydride, itaconic anhydride, monoethyl maleate, monoethyl fumarate, monoethyl itaconate, diethyl maleate, diethyl fumarate and diethyl itaconate etc.
Examples of monomers having both hydroxyl group and carboxyl group (A) include hydroxyalkyl (meth)acrylic acids, specifically xcex2-oxy(meth)acrylic acid etc.
Any monomer can be selected, within such limits that the effects of the present invention will not be marred, for the monomer (B) that may be copolymerized with the above-described monomers when necessary. Examples of such monomers include styrene derivatives, (meth)acrylate derivatives (e.g., alkyl (meth)acrylate, cycloalkyl (meth)acrylate, aryl (meth)acrylate, etc.), monoolefinic unsaturated compounds, and conjugated diolefinic hydrocarbons etc. Specific examples of these monomers include styrene, xcex1- or xcex2-methylstyrene, o-, m- or p-methylstyrene, p-methoxystyrene, (meth) acrylonitrile, vinyl chloride, vinylidene chloride, (meth)acrylamide, vinyl acetate, methyl (meth)acrylate, ethyl (meth)acrylate, n-, sec- or tert-butyl (meth)acrylate, iso-propyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-methylcyclohexyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, 1,3-butadiene, chloroprene, isoprene and dimethylbutadiene etc.
Monomers having hydroxyl group itself and/or carboxyl group itself have been exemplified as monomers useful for obtaining the polymer for use in the present invention. However, the polymer may also be produced by copolymerizing or homopolymerizing monomers whose hydroxyl and/or carboxyl group is protected by a protective group, thereby obtaining a polymer, and then removing the protecting group to finally obtain the desired polymer having hydroxyl group and/or carboxyl group. In this case, monomers that can be the source of carboxyl or hydroxyl group may be used as the monomer (B). For instance, a copolymer having carboxyl group can be obtained by hydrolyzing a methyl methacrylate copolymer.
In a second embodiment of the present invention, the photosensitive resin composition comprises as the alkali-soluble polymer a polymer having hydroxyl group and a polymer having carboxyl group. A combination of any polymer having hydroxyl group and any polymer having carboxyl group can be used for the second photosensitive resin composition of the present invention. However, the OH value of the polymer having hydroxyl group is preferably from 10 to 180, more preferably from 50 to 120; and the acid value of the polymer having carboxyl group is preferably from 10 to 200, more preferably from 30 to 150.
These polymers can be obtained by polymerizing monomers that can be used for producing the above-described polymer for use in the photosensitive resin composition. Namely, a polymer having hydroxyl group can be obtained by homopolymerizing the above-described monomer having hydroxyl group (A1), or by copolymerizing the monomer (A1) and the above-described monomer (B); and a polymer having carboxyl group can be obtained by homopolymerizing the above-described monomer having carboxyl group (A2), or by copolymerizing the monomer (A2) and the monomer (B).
There is no particular limitation on the molecular weight of the polymer for use in the photosensitive resin composition of the present invention. However, the weight-average molecular weight of the polymer is generally from 5,000 to 100,000, preferably from 5,000 to 40,000.
In the first or second photosensitive resin composition of the present invention, a combination of two or more resin compositions can be used. Further, polymers other than the resin compositions may be incorporated into the resin compositions when necessary.
The polymer content of the photosensitive resin composition of the present invention is from 3 to 80%, preferably from 10 to 35% of the total weight of the photosensitive resin composition. When the polymer content is within the above-described range, a sufficiently hardened film is obtained after development, and also a satisfactorily high contrast is obtained after development.
3. Crosslinking Agent
The photosensitive resin composition of the present invention comprises a crosslinking agent. This crosslinking agent serves to crosslink hydroxyl group and carboxyl group present in the polymer used. By this crosslinking reaction which occurs during post baking (which will be described later in detail) to be usually conducted after development, the photosensitive resin composition of the present invention is finally hardened to give a film having sufficiently high strength.
Such a crosslinking agent can be selected from conventional crosslinking agents, for example, those of epoxy type, isocyanate type, phenol type or amine type, and acid anhydrides.
Specific examples of useful crosslinking agents include bisphenol acetone diglycidyl ether, phenol novolak epoxy resins, cresol novolak epoxy resins, triglycidyl isocyanurate, tetraglycidyldiaminodiphenylene, tetraglycidyl-m-xylene-diamine, tetraglycidyl-1,3-bis(aminoethyl)cyclohexane, tetraphenylglycidyl ether ethane, triphenyl glycidyl ether ethane, bisphenol hexafluoroacetodiglycidyl ether, 1,3-bis(1-(2,3-epoxypropoxy)-1-trifluoromethyl-2,2,2-trifluoro-methyl)benzene, 4,4-bis(2,3-epoxypropoxy)octafluorobiphenyl, triglycidyl-p-aminophenol, tetraglycidylmetaxylenediamine, 2-(4-(2,3-epoxypropoxy)phenyl)-2-(4-(1,1-bis(4-(2,3-epoxy-propoxy)phenyl)ethyl)phenyl)propane, and 1,3-bis(4-(1-(4-(2,3-epoxypropoxy)phenyl)-1-(4-(1-(4-(2,3-epoxypropoxy-phenyl)-1-methylethyl)phenyl)ethyl)phenoxy)-2-propanol etc.
These crosslinking agents are used singly, and, if necessary, two or more of these crosslinking agents may be used in combination.
4. Solvent
A solvent is used for the photosensitive resin composition of the present invention in order to dissolve in the solvent the aforementioned photosensitizer, polymer and crosslinking agent, and other components that are added as needed. Any purposive solvent can be used as this solvent, and a solvent selected from glycol ethers, cellosolve esters, aromatic hydrocarbons, ketones, propylene glycols and esters is generally used.
Specific examples of useful organic solvents include propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol t-butyl ether, dipropylene glycol methyl ether, dipropylene glycol propyl ether, tripropylene glycol methyl ether, propylene glycol methyl ether acetate, dipropylene glycol methyl ether acetate, ethylene glycol ethyl ether, ethylene glycol methyl ether, ethylene glycol butyl ether, ethylene glycol isopropyl ether, ethylene glycol n-butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monoacetate, diethylene glycol monoethyl ether acetate, propylene glycol phenyl ether, propylene glycol ethyl ether acetate, triethylene glycol butyl ether, cellosolve acetate, methyl cellosolve acetate, ethyl cellosolve acetate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutanol, ethyl lactate, methyl lactate, butyl lactate, pentyl lactate, butyl acetate, amyl formate, isoamyl acetate, isobutyl acetate, methoxybutyl acetate, butyl propionate, isobutyl lactate, butyl lactate, ethyl pyruvate, toluene, xylene, methyl ethyl ketone and cyclohexanone.
These solvents can be used either singly or in combination of two or more members.
5. Photosensitive Resin Composition
The photosensitive resin composition of the present invention can be prepared by adding to and dissolving in the solvent the above-described photosensitizer, polymer and crosslinking agent, and, if necessary, additives such as surface active agents, alkali-dissolution promoters, alkali-dissolution inhibitors and antioxidants. These components can be added to the solvent in any order. Moreover, the photosensitive resin composition may also be prepared by separately dissolving the components in different solvents, and mixing the resulting solutions upon use. Further, although stirring is generally used to dissolve the components in the solvent, any other means such as the application of ultrasound may be employed in combination with stirring.
The photosensitive resin composition of the present invention can be applied to the surface of a substrate by any conventional method. Specifically, the photosensitive resin composition of the present invention can be applied by means of spray coating, roll coating, spin coating, dip coating, curtain coating or the like. There is no particular limitation on the substrate to be coated with the photosensitive resin composition of the present invention. Examples of useful substrates include semiconductor devices, color filters, TFTs, glass, glass filters, black matrixes, a variety of polymers (e.g., polyimide, polyamide, polyethylene, acrylic resins, etc.), silicon nitride, metallic oxides (titanium oxide, silicon oxide, chromium oxide, indium titanium oxide, etc.), and metals (e.g., aluminum, copper, etc.).
In general, the photosensitive resin composition of the present invention applied to the substrate is then subjected to pre-baking. The purpose of this pre-baking treatment is to remove all of or part of the solvent contained in the photosensitive resin composition film formed on the substrate. By this treatment, the photosensitive resin composition film is fixed to the substrate, so that the film is prevented from separating from the substrate during the succeeding light exposure and development treatments. The pre-baking treatment can be conducted under any condition as long as the above-described purpose can be attained. In general, however, this treatment is conducted by heating the photosensitive resin composition film at a temperature of 50 to 120xc2x0 C. for 30 seconds to 2 minutes.
After conducting the pre-baking treatment, the photosensitive resin composition film provided on the substrate is exposed to actinic rays having a wavelength at which the photosensitizer is sensitive. Ultraviolet light with a wavelength of 250 to 500 nm is usually used as the actinic rays. It is preferable to use as this ultraviolet light i- or g-line emitted by a mercury vapor lamp, and i-line are particularly preferred. Further, the amount of light energy to be applied during this exposure is so controlled that crosslinking reaction can fully proceed in the exposed area, and it is generally in the range of 10 to 500 mJ/cm2.
The exposure can be conducted by any conventional method; for example, exposure through a photomask, scanning exposure using a stepper, or the like can be used.
In general, the photosensitive resin composition film that has been exposed to light is then developed by an alkaline solution. By this development, the area on the photosensitive resin composition film that has been exposed to actinic rays is removed, and a positive image can thus be obtained. Any conventional developer useful for developing photoresists can be herein used. In general, an aqueous solution of an inorganic alkaline compound, primary amine, secondary amine, tertiary amine, alcohol amine or quaternary ammonium salt is used. More specifically, an aqueous solution of tetramethylammonium hydride (hereinafter referred to as xe2x80x9cTMAHxe2x80x9d), potassium hydroxide, sodium hydroxide, sodium carbonate, sodium silicate, ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethanolamine, dimethylethanolamine, tetramethylammonium, tetraethylammonium or choline can be used as the developer. Further, any additive selected from water-soluble organic solvents (specifically, methanol, ethanol, etc.), surface active agents and the like may be added to the developer, if necessary.
In general, the photosensitive resin composition film that has been developed is then subjected to post-baking. The purpose of this post-baking treatment is to obtain a sufficiently hardened positive image in a desired shape by heating the photosensitive resin composition film remaining on the substrate after development. The post-baking treatment can be conducted under any condition as long as the above purpose can be attained. However, the post-baking treatment is generally conducted by treating the photosensitive resin composition film at a temperature of 100 to 250xc2x0 C. for 30 minutes to 2 hours.
An ordinary method for forming a positive image by using the photosensitive resin composition of the present invention has been described hereinbefore. In addition to the above-described treatments included in this method, other treatments usually used for treating photoresists, for instance, washing and drying of a photosensitive resin composition film may optionally be conducted.
Films formed in the aforementioned manner by using the photosensitive resin composition of the present invention have extremely high transparency. Moreover, images or patterns formed in these films have satisfactorily high contrast. Therefore, the films made from the photosensitive resin composition of the present invention can be used similarly as in the case of conventional photoresist films. In addition, by utilizing their advantageous properties, these films can suitably be used, for example, as protective-insulating films for semiconductor devices, liquid crystal devices, FPDs or the like, as protective films for color filters, and as protective or insulating films for TFTs.
The present invention will now be described more specifically by referring to the following examples, which are given for illustration of the invention and are not intended to be limiting thereof.